Changing return type in generated CS function using SWIG

Question

I am trying to generate wrappers in C# for C++ library and using generated C3 wrappers I am developing client application.

C++ class:

namespace ns {
    class ISampleInterface {
        public:
            virtual ~ISampleInterface() {}
            virtual void fn(int cnt) = 0;
    };
}

namespace ns {
    class ISampleInterface2 {
        public:
            virtual ~ISampleInterface() {}
            virtual void fn2(int cnt) = 0;
    };
}

namespace ns {
    class SampleClass  {
        public:
            SampleClass() {}
            ~SampleClass() {}
            void InputFunction(int count, ISampleInterface sampleInterface, ISampleInterface2& sampleInterface2){
            }
            ISampleInterface& OutputFunction(void) {
                return null;
            }
    };
}

Expected C# code:

namespace csNS {
    public class SampleClass {
        public void InputFunction(int count, out SampleInterface sampleInterface, out SampleInterface2 sampleInterface2) {
            // some code
        }
        public SampleInterface OutputFunction() {
            // some code 
        }
    }
}

Swig interface declaration:

%interface_custom("SampleInterfaceImpl", "SampleInterface", ns::ISampleInterface);
%interface_custom("SampleInterface2Impl", "SampleInterface2", ns::ISampleInterface2);

%Outparams(ns:ISampleInterface, SampleInterfaceImpl)
%Outparams(ns:ISampleInterface2, SampleInterface2Impl)

In above C# code, InputFunction takes 3 arguments. However, the implementation generated for SampleInterface and SampleInterface2 does not contain default constructor. Hence I can not create objects for these interfaces. As I am unable to instantiate interfaces at C# side, I want to pass then as out parameter to the CS function and then that will be initialized at C++ side. So to modify cs file generated during swig compilation below typemap I had defined.

Typemap declarations:

%define %Outparams(TYPE, InterfaceImpl)

%typemap (cstype) TYPE,
                  TYPE &,
                  TYPE *,
                  TYPE *& "out TYPE"
%enddef

Using above typemap I am able to change input arguments, however, it is also changing function return values and I am not able to control this.

Actual cs code generated:

namespace csNS {
    public class SampleClass {
        public void InputFunction(int count, out SampleInterface sampleInterface, out SampleInterface2 sampleInterface2) {
            // some code
        }
        public out SampleInterface OutputFunction() {
            // some code 
        }
    }
}

What am I doing wrong???

Answer 1

I changed typemap declaration, It worked.

For class:

%typemap (cstype, out="TYPE") TYPE,
                  TYPE &,
                  TYPE *,
                  TYPE *& "out TYPE" 

For Interface:

%typemap (cstype, out="InterfaceImpl") TYPE,
                  TYPE &,
                  TYPE *,
                  TYPE *& "out InterfaceImpl"

CS file:

namespace csNS {
    public class SampleClass {
        public void InputFunction(int count, out SampleInterface sampleInterface, out SampleInterface2 sampleInterface2) {
            // some code
        }
        public SampleInterfaceImpl OutputFunction() {
            // some code 
        }
    }
}